It is known that the placing of wells in production in sandy deposits, with the aid of horizontal or slightly sloping drains, results in the sand being carried by the fluid flowing from the deposit and results in large deposits of sand or other sediments, mainly in the horizontal part of the drains. This causes a considerable decrease in the production of the well and sometimes makes it impossible to introduce measuring or intervention tools down into the drain.
U.S. Pat. No. 4,744,420 describes a known device for cleaning such horizontal drains which includes, at the end of two concentric pipe columns, a body fitted with nozzles for projecting a cleaning fluid, this body delimiting a cleaning fluid feeding passage connected to said nozzles, as well as a passage for the return of this fluid loaded with solid particles of sand or other sediments, these two passages being respectively connected to one of the two pipes delimited by the two concentric pipe columns.
In this known device, the nozzles for projecting cleaning fluid are disposed at the end of the body and are orientated substantially parallel to the axis of the drain. Such a lay-out tends to expel in front of the device the sand and other sediments accumulated in the drain.
It is this particular problem which the invention proposes to resolve so as to carry out a more effective cleaning of such horizontal drains.
European Patent No. 417,009 mentions a known device including deflecting means adapted for directing the cleaning fluid jet coming out of a nozzle in the direction of the wall of the drain.
The deflector may however be a mechanically fragile part with certain dimensions of the device. Besides, the equipment does not allow the distance between the turbulence zone of the cleaning fluid at the outlet of the nozzle and the suction zone to be adjusted.
It has been established that adjusting this distance is important because it conditions the proper return circulation towards the sucking device of the fluid loaded with sediments. In fact, the purpose of the fluid spurting out of the outlet ports is to stir and to carry along the sediments towards the sucking device. To this effect, the outlet ports are disposed, with respect to the suction ports, in such a way that the stirring turbulences are sufficiently distant from the suction ports in order not to impede the direction of circulation of the fluid intended to carry along the sediments, and at the same time close enough for the suction effect to act effectively on the fluid loaded with sediments suspended by said turbulences.
The parameters acting upon this distance may be notably the available rate of circulation of the fluid, the mean viscosity of the fluid loaded with sediments, the diameter of the drain, the density of the sediments or the rheology of the cleaning fluid.